排序方式： 共有8条查询结果，搜索用时 296 毫秒
1
1.
Bougrain Laurent Gonzalez Maria Bouchot Vincent Cassard Daniel Lips Andor L. W. Alexandre Frédéric Stein Gilbert 《Natural Resources Research》2003,12(3):173-181
This study is concerned with understanding of the formation of ore deposits (precious and base metals) and contributes to the exploration and discovery of new occurrences using artificial neural networks. From the different digital data sets available in BRGM's GIS Andes (a comprehensive metallogenic continental-scale Geographic Information System) 25 attributes are identified as known factors or potential factors controlling the formation of gold deposits in the Andes Cordillera. Various multilayer perceptrons were applied to discriminate possible ore deposits from barren sites. Subsequently, because artificial neural networks can be used to construct a revised model for knowledge extraction, the optimal brain damage algorithm by LeCun was applied to order the 25 attributes by their relevance to the classification. The approach demonstrates how neural networks can be used efficiently in a practical problem of mineral exploration, where general domain knowledge alone is insufficient to satisfactorily model the potential controls on deposit formation using the available information in continent-scale information systems. 相似文献
2.
Vincent Bouchot Patrick Ledru Catherine Lerouge Jean-Luc Lescuyer Jean-Pierre Milesi 《Ore Geology Reviews》2005,27(1-4):169
The French Massif Central constitutes an exceptional study area due to the diversity of its metallic deposits, its internal position in the Variscan belt, and the abundance of available geological, geophysical and metallogenic data obtained within the GeoFrance 3D programme. The deposits, formed towards the end of the orogenic evolution, represent the economic products of two distinct mineralizing systems, a Au ± Sb hydrothermal system and a W ± Sn and rare-metals magmatic–hydrothermal system, which were simultaneously active during a short time span between ca. 310 and 300 Ma.Two types of gold deposit can be distinguished on the basis of their depth of emplacement: “deep-seated” gold deposits developed under lithostatic to hydrostatic pressure during rapid exhumation, and “shallow” gold deposits emplaced under hydrostatic pressure with no significant uplift.Deposits of W ± Sn and rare-metals were emplaced in the upper crust during final crystallization of specialized magmas after their rapid ascent, perhaps enhanced by simultaneous regional uplift. The gold-bearing systems are associated with a complex network of re-activated crustal-scale faults initially active during the period between 335 and 315 Ma. Normal motion along the faults, coeval with 335 to 315 Ma granite–migmatite domes, played a major role in the 3D distribution of the hydrothermal plumbing system. Gold and related metals were carried within huge hydrothermal cells, which reached ca. 100 km by 10 km in area, and 30 km in depth. In contrast, granites rich in magmatophile elements (W, Sn, rare-metals) generated smaller hydrothermal cells (10 km by 10 km in area, and < 6 km deep). Extraction of metals, by both deep-seated fluids and specialized magmas, occurred during granulitization of the lower crust at 300 ± 15 Ma. In the French Massif Central, the genesis of the two late Carboniferous mineralizing systems coincided with the end of syn-collisional extension and ended just before post-collisional extension. 相似文献
3.
A. Chauvet N. Volland-Tuduri C. Lerouge V. Bouchot P. Monié X. Charonnat M. Faure 《International Journal of Earth Sciences》2012,101(1):69-86
Geochronological, mineralogical, and geochemical analyses have been focussed on the Mont-Lozère-Borne plutonic complex and
surrounding rocks (Cévennes, French Massif Central) in which B–W-Sn and As-Au-Sb mineralization is encountered. Two main results
are highlighted: (1) the existence of a 301–306 Ma magmato-hydrothermal event unrelated to the emplacement of the Pont-de-Montvert-Borne
plutonic body at 316 Ma; (2) the magmatic and hydrothermal features are strongly associated, both in time and in space, thus
demonstrating an intimate connection between mineralizing processes and magmatism in this part of the French Massif Central.
We also show that mineralization and associated hydrothermal occurrences do not correspond to a simple and single geochemical
signature and that a contamination model must be invoked in order to account for the complexity of isotopic results. This
study demonstrates that the application of the O and H isotopic signatures as tracers of the source and nature of fluids in
an orogenic context requires some specific care. Finally, a model of the tectonic-magmatic-hydrothermal evolution of the study
area is suggested in which we discuss two alternative scenarios. The first one implies the existence of two different hydrothermal/mineralizing
events (Bo-W-Sn and As-Au-Sb ones). The second one suggests the same source for all hydrothermal and mineralized structures. 相似文献
4.
Jean-Philippe Bellot Laurent Bailly Catherine Lerouge Vincent Bouchot 《Mineralium Deposita》2004,39(5-6):576-582
The natural deformation of stibnite in relation to the kinematic history of a regional fault is resolved using microstructural analysis of massive stibnite along the Biards Fault in the Massif Central (France). Stibnite underwent intra-crystalline deformation associated with a strong linear and planar anisotropy. Lepidoblastic textures, undulatory extinction of oriented grains, growth of antimony between these grains, and a colour change of stibnite from white to black, result from dynamic recrystallisation. A range of asymmetric microstructures indicate non-coaxial deformation and a left-lateral sense of shear, related to the movement of the fault zone. The computed displacement corresponds to the geological offsets measured along the fault. We conclude that stibnite has microstructurally recorded the bulk kinematics of its host fault zone.Editorial Handling: F. Tornos 相似文献
5.
Laurent Désindes Marc Durand Laurent Bailly Stéphane Jaillet Vincent Bouchot Marc Lespinasse Marcel Pouliquen Jean-Michel Ostermann Jacques Leroy 《International Journal of Earth Sciences》2006,95(1):80-94
This article describes the formation of the principal French high-purity silica placer (source for electrometallurgy of silicon and ferrosilicon), the Boudeau deposit in Dordogne, and of one of its subordinate deposits, the Pays Brûlé deposit. Boudeau has always been considered to be a colluvial deposit, formed in a trap produced by extensional tectonism. The present work suggests a new genetic interpretation, based on a combined study of the deposits and their underlying rocks. It shows that the quartz gravel deposits, laid down by stream flow within braided channels, were reworked by karstic progressive sinking, and that the mechanism responsible for the increase in the thickness of the economic formations is cryptokarstic corrosion. This undercovers weathering process, which involves dissolution of karstifiable rocks (oolitic and bioclastic limestones) at their interface with a permeable, non-karstifiable cover composed of chemically pure quartz gravels in a sandy-argillaceous matrix. A typological study of the gravels provides a basis for tackling the problem of their origin and their purity. They seem to be derived mainly from the synmetamorphic quartz mobilisates of the stripped metamorphic units (the lower and upper gneiss units forming the western edge of the Massif Central). Lastly, a dynamic model is suggested for the genesis of the high-purity silica deposits of Dordogne. 相似文献
6.
The Le Châtelet gold deposit is unique among the mined deposits of the French Variscan basement in that the gold is not free but caught up in the arsenopyrite crystal lattice. Microstructural analysis shows that the Au-arsenopyrite quartz veins are hosted by north-trending dextral strike-slip faults resulting from NNE-SSW compression during the early Stephanian (around 300 Ma). Textural study indicates that vein emplacement was due to sequential dynamics related to spasmodic strike-slip movements along these brittle structures (seismic regime). The classic sequence begins with the slow crystallization of sulphide-free comb quartz followed by a co-deposition of microcrystalline quartz and needles of Au-arsenopyrite; the rapid crystallization of the Au-arsenopyrite-bearing microcrystalline quartz was due to a sudden drop in fluid pressure. The veins correspond to dilational jogs formed by a suction pump mechanism during a late phase of the Variscan orogeny; they were trapped in migmatite about 1 km below surface. 相似文献
7.
8.
J.P. Milesi S.F. Toteu Y. Deschamps J.L. Feybesse C. Lerouge A. Cocherie J. Penaye R. Tchameni G. Moloto-A-Kenguemba H.A.B. Kampunzu N. Nicol E. Duguey J.M. Leistel M. Saint-Martin F. Ralay C. Heinry V. Bouchot J.C. Doumnang Mbaigane V. Kanda Kula F. Chene J. Monthel P. Boutin J. Cailteux 《Journal of African Earth Sciences》2006,44(4-5):571
This paper is prepared within the frameworks of IGCP Project 470 and the associated BRGM scientific project “Africa 1999–2004” to accompany the 1:4,000,000 scale map “Geology and major ore deposits of Central Africa, presented at the 20th Colloquium of African Geology in Orleans in June 2004. It incorporates geological and metallogenic data from eight countries in Central Africa (Angola, Cameroon, Chad, Central African Republic, Congo Brazzaville, Democratic Republic of Congo (DRC), Equatorial Guinea and Zambia). The map is a harmonised and geo-referenced preliminary map, based on a GIS at 1:2,000,000 scale, and focusses on the spatial and temporal distribution of selected major deposits. 相似文献
1